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<H1 class="no-header">curs_color 3x 2023-09-16 ncurses 6.4 Library calls</H1>
<PRE>
<STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>                   Library calls                  <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>




</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
       <STRONG>start_color</STRONG>,   <STRONG>has_colors</STRONG>,   <STRONG>can_change_color</STRONG>,  <STRONG>init_pair</STRONG>,  <STRONG>init_color</STRONG>,
       <STRONG>init_extended_pair</STRONG>, <STRONG>init_extended_color</STRONG>,  <STRONG>color_content</STRONG>,  <STRONG>pair_content</STRONG>,
       <STRONG>extended_color_content</STRONG>,    <STRONG>extended_pair_content</STRONG>,    <STRONG>reset_color_pairs</STRONG>,
       <STRONG>COLOR_PAIR</STRONG>, <STRONG>PAIR_NUMBER</STRONG> - manipulate terminal colors with <EM>curses</EM>


</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
       <STRONG>#include</STRONG> <STRONG>&lt;curses.h&gt;</STRONG>

       <STRONG>int</STRONG> <STRONG>start_color(void);</STRONG>

       <STRONG>bool</STRONG> <STRONG>has_colors(void);</STRONG>
       <STRONG>bool</STRONG> <STRONG>can_change_color(void);</STRONG>

       <STRONG>int</STRONG> <STRONG>init_pair(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_color(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <EM>b</EM><STRONG>);</STRONG>
       /* extensions */
       <STRONG>int</STRONG> <STRONG>init_extended_pair(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>init_extended_color(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <EM>b</EM><STRONG>);</STRONG>

       <STRONG>int</STRONG> <STRONG>color_content(short</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>pair_content(short</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>short</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       /* extensions */
       <STRONG>int</STRONG> <STRONG>extended_color_content(int</STRONG> <EM>color</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>r</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>g</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>
       <STRONG>int</STRONG> <STRONG>extended_pair_content(int</STRONG> <EM>pair</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>f</EM><STRONG>,</STRONG> <STRONG>int</STRONG> <STRONG>*</STRONG><EM>b</EM><STRONG>);</STRONG>

       /* extensions */
       <STRONG>void</STRONG> <STRONG>reset_color_pairs(void);</STRONG>

       <STRONG>int</STRONG> <STRONG>COLOR_PAIR(int</STRONG> <EM>n</EM><STRONG>);</STRONG>
       <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM><STRONG>);</STRONG>


</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>

</PRE><H3><a name="h3-Overview">Overview</a></H3><PRE>
       <STRONG>curses</STRONG> supports color attributes on terminals with that capability.  To
       use  these  routines  <STRONG>start_color</STRONG>  must  be called, usually right after
       <STRONG>initscr</STRONG>.  Colors are always used in pairs (referred to as color-pairs).
       A  color-pair  consists  of  a  foreground color (for characters) and a
       background color (for the blank  field  on  which  the  characters  are
       displayed).   A  programmer  initializes  a color-pair with the routine
       <STRONG>init_pair</STRONG>.  After it has been initialized, <STRONG>COLOR_PAIR</STRONG>(<EM>n</EM>) can be used to
       convert the pair to a video attribute.

       If  a  terminal is capable of redefining colors, the programmer can use
       the routine <STRONG>init_color</STRONG> to  change  the  definition  of  a  color.   The
       routines   <STRONG>has_colors</STRONG>   and  <STRONG>can_change_color</STRONG>  return  <STRONG>TRUE</STRONG>  or  <STRONG>FALSE</STRONG>,
       depending on whether the terminal has color  capabilities  and  whether
       the programmer can change the colors.  The routine <STRONG>color_content</STRONG> allows
       a programmer to extract the amounts of red, green, and blue  components
       in  an initialized color.  The routine <STRONG>pair_content</STRONG> allows a programmer
       to find out how a given color-pair is currently defined.


</PRE><H3><a name="h3-Color-Rendering">Color Rendering</a></H3><PRE>
       The  <STRONG>curses</STRONG>  library  combines  these  inputs  to  produce  the  actual
       foreground and background colors shown on the screen:

       <STRONG>o</STRONG>   per-character video attributes (e.g., via <STRONG>waddch</STRONG>),

       <STRONG>o</STRONG>   the window attribute (e.g., by <STRONG>wattrset</STRONG>), and

       <STRONG>o</STRONG>   the background character (e.g., <STRONG>wbkgdset</STRONG>).

       Per-character  and  window  attributes  are  usually set by a parameter
       containing  video  attributes  including  a  color  pair  value.   Some
       functions such as <STRONG>wattr_set</STRONG> use a separate parameter which is the color
       pair number.

       The background character is a special case:  it  includes  a  character
       value, just as if it were passed to <STRONG>waddch</STRONG>.

       The  <STRONG>curses</STRONG> library does the actual work of combining these color pairs
       in an internal function called from <STRONG>waddch</STRONG>:

       <STRONG>o</STRONG>   If the parameter passed to <STRONG>waddch</STRONG> is <EM>blank</EM>, and it uses the special
           color pair 0,

           <STRONG>o</STRONG>   <STRONG>curses</STRONG> next checks the window attribute.

           <STRONG>o</STRONG>   If  the window attribute does not use color pair 0, <STRONG>curses</STRONG> uses
               the color pair from the window attribute.

           <STRONG>o</STRONG>   Otherwise, <STRONG>curses</STRONG> uses the background character.

       <STRONG>o</STRONG>   If the parameter passed to <STRONG>waddch</STRONG> is <EM>not</EM> <EM>blank</EM>, or it does not  use
           the  special  color  pair 0, <STRONG>curses</STRONG> prefers the color pair from the
           parameter, if it  is  nonzero.   Otherwise,  it  tries  the  window
           attribute next, and finally the background character.

       Some  <STRONG>curses</STRONG>  functions  such  as  <STRONG>wprintw</STRONG>  call  <STRONG>waddch</STRONG>.  Those do not
       combine its parameter with a color pair.  Consequently those calls  use
       only the window attribute or the background character.


</PRE><H2><a name="h2-CONSTANTS">CONSTANTS</a></H2><PRE>
       In <STRONG>&lt;curses.h&gt;</STRONG> the following macros are defined.  These are the standard
       colors (ISO-6429).  <STRONG>curses</STRONG> also assumes that <STRONG>COLOR_BLACK</STRONG> is the default
       background color for all terminals.

             <STRONG>COLOR_BLACK</STRONG>
             <STRONG>COLOR_RED</STRONG>
             <STRONG>COLOR_GREEN</STRONG>
             <STRONG>COLOR_YELLOW</STRONG>
             <STRONG>COLOR_BLUE</STRONG>
             <STRONG>COLOR_MAGENTA</STRONG>
             <STRONG>COLOR_CYAN</STRONG>
             <STRONG>COLOR_WHITE</STRONG>

       Some  terminals  support  more than the eight (8) "ANSI" colors.  There
       are no standard names for those additional colors.


</PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>

</PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
       is initialized by <STRONG>start_color</STRONG> to  the  maximum  number  of  colors  the
       terminal can support.


</PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
       is  initialized by <STRONG>start_color</STRONG> to the maximum number of color pairs the
       terminal can support.


</PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>

</PRE><H3><a name="h3-start_color">start_color</a></H3><PRE>
       The <STRONG>start_color</STRONG> routine requires no arguments.  It must  be  called  if
       the  programmer  wants  to  use  colors,  and  before  any  other color
       manipulation routine is called.  It  is  good  practice  to  call  this
       routine right after <STRONG>initscr</STRONG>.  <STRONG>start_color</STRONG> does this:

       <STRONG>o</STRONG>   It   initializes  two  global  variables,  <STRONG>COLORS</STRONG>  and  <STRONG>COLOR_PAIRS</STRONG>
           (respectively defining the maximum number of colors and color-pairs
           the terminal can support).

       <STRONG>o</STRONG>   It  initializes  the special color pair <STRONG>0</STRONG> to the default foreground
           and background colors.  No other color pairs are initialized.

       <STRONG>o</STRONG>   It restores the colors on the terminal to the values they had  when
           the terminal was just turned on.

       <STRONG>o</STRONG>   If  the  terminal supports the <STRONG>initc</STRONG> (<STRONG>initialize_color</STRONG>) capability,
           <STRONG>start_color</STRONG> initializes its internal table  representing  the  red,
           green, and blue components of the color palette.

           The components depend on whether the terminal uses CGA (aka "ANSI")
           or HLS (i.e.,  the  <STRONG>hls</STRONG>  (<STRONG>hue_lightness_saturation</STRONG>)  capability  is
           set).   The  table  is  initialized  first  for  eight basic colors
           (black, red, green, yellow, blue, magenta, cyan, and white),  using
           weights that depend upon the CGA/HLS choice.  For "ANSI" colors the
           weights are <STRONG>680</STRONG> or <STRONG>0</STRONG> depending on whether  the  corresponding  red,
           green,  or  blue component is used or not.  That permits using <STRONG>1000</STRONG>
           to represent bold/bright colors.  After the  initial  eight  colors
           (if  the  terminal  supports more than eight colors) the components
           are initialized using the same pattern, but with weights  of  <STRONG>1000</STRONG>.
           SVr4 uses a similar scheme, but uses <STRONG>1000</STRONG> for the components of the
           initial eight colors.

           <STRONG>start_color</STRONG> does not attempt to set the terminal's color palette to
           match  its  built-in  table.   An application may use <STRONG>init_color</STRONG> to
           alter the internal table along with the terminal's color.

       These limits apply to color values and  color  pairs.   Values  outside
       these limits are not legal, and may result in a runtime error:

       <STRONG>o</STRONG>   <STRONG>COLORS</STRONG>   corresponds   to   the   terminal   database's  <STRONG>max_colors</STRONG>
           capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).

       <STRONG>o</STRONG>   color values are expected  to  be  in  the  range  <STRONG>0</STRONG>  to  <STRONG>COLORS-1</STRONG>,
           inclusive (including <STRONG>0</STRONG> and <STRONG>COLORS-1</STRONG>).

       <STRONG>o</STRONG>   a  special  color value <STRONG>-1</STRONG> is used in certain extended functions to
           denote the <EM>default</EM> <EM>color</EM> (see <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>).

       <STRONG>o</STRONG>   <STRONG>COLOR_PAIRS</STRONG>  corresponds  to  the  terminal  database's   <STRONG>max_pairs</STRONG>
           capability, (see <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>).

       <STRONG>o</STRONG>   legal  color  pair  values  are  in  the  range <STRONG>1</STRONG> to <STRONG>COLOR_PAIRS-1</STRONG>,
           inclusive.

       <STRONG>o</STRONG>   color pair <STRONG>0</STRONG> is special; it denotes "no color".

           Color pair <STRONG>0</STRONG> is assumed to be  white  on  black,  but  is  actually
           whatever  the  terminal implements before color is initialized.  It
           cannot be modified by the application.


</PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
       The <STRONG>has_colors</STRONG> routine requires no arguments.  It returns <STRONG>TRUE</STRONG>  if  the
       terminal  can  manipulate  colors;  otherwise,  it returns <STRONG>FALSE</STRONG>.  This
       routine  facilitates  writing   terminal-independent   programs.    For
       example, a programmer can use it to decide whether to use color or some
       other video attribute.


</PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
       The <STRONG>can_change_color</STRONG> routine requires no arguments.  It returns <STRONG>TRUE</STRONG> if
       the  terminal  supports colors and can change their definitions; other,
       it  returns  <STRONG>FALSE</STRONG>.   This  routine   facilitates   writing   terminal-
       independent programs.


</PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
       The <STRONG>init_pair</STRONG> routine changes the definition of a color-pair.  It takes
       three arguments: the number  of  the  color-pair  to  be  changed,  the
       foreground color number, and the background color number.  For portable
       applications:

       <STRONG>o</STRONG>   The first argument must be a legal color pair  value.   If  default
           colors  are  used  (see  <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>) the upper limit is
           adjusted to allow for extra pairs which  use  a  default  color  in
           foreground and/or background.

       <STRONG>o</STRONG>   The second and third arguments must be legal color values.

       If  the  color-pair was previously initialized, the screen is refreshed
       and  all  occurrences  of  that  color-pair  are  changed  to  the  new
       definition.

       As  an  extension,  ncurses  allows  you  to  set  color pair <STRONG>0</STRONG> via the
       <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG> routine, or to specify  the  use  of  default
       colors (color number <STRONG>-1</STRONG>) if you first invoke the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG>
       routine.


</PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
       Because <STRONG>init_pair</STRONG> uses signed <STRONG>short</STRONG>s for its  parameters,  that  limits
       color-pairs   and  color-values  to  32767  on  modern  hardware.   The
       extension <STRONG>init_extended_pair</STRONG> uses <STRONG>int</STRONG>s for the  color-pair  and  color-
       value, allowing a larger number of colors to be supported.


</PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
       The  <STRONG>init_color</STRONG>  routine  changes  the definition of a color.  It takes
       four arguments: the number of the color to be changed followed by three
       RGB values (for the amounts of red, green, and blue components).

       <STRONG>o</STRONG>   The  first argument must be a legal color value; default colors are
           not allowed here.  (See the section <STRONG>Colors</STRONG> for  the  default  color
           index.)

       <STRONG>o</STRONG>   Each  of  the  last  three arguments must be a value in the range <STRONG>0</STRONG>
           through <STRONG>1000</STRONG>.

       When <STRONG>init_color</STRONG> is used, all occurrences of that color  on  the  screen
       immediately change to the new definition.


</PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
       Because  <STRONG>init_color</STRONG>  uses signed <STRONG>short</STRONG>s for its parameters, that limits
       color-values and their red, green, and  blue  components  to  32767  on
       modern  hardware.   The extension <STRONG>init_extended_color</STRONG> uses <STRONG>int</STRONG>s for the
       color value and for  setting  the  red,  green,  and  blue  components,
       allowing a larger number of colors to be supported.


</PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
       The <STRONG>color_content</STRONG> routine gives programmers a way to find the intensity
       of the red, green, and blue (RGB) components in a color.   It  requires
       four  arguments:  the  color  number, and three addresses of <STRONG>short</STRONG>s for
       storing the information about the  amounts  of  red,  green,  and  blue
       components in the given color.

       <STRONG>o</STRONG>   The  first  argument  must  be a legal color value, i.e., <STRONG>0</STRONG> through
           <STRONG>COLORS-1</STRONG>, inclusive.

       <STRONG>o</STRONG>   The values that are stored at the addresses pointed to by the  last
           three  arguments  are  in  the  range <STRONG>0</STRONG> (no component) through <STRONG>1000</STRONG>
           (maximum amount of component), inclusive.


</PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
       Because <STRONG>color_content</STRONG> uses  signed  <STRONG>short</STRONG>s  for  its  parameters,  that
       limits  color-values and their red, green, and blue components to 32767
       on modern hardware.  The extension <STRONG>extended_color_content</STRONG> uses <STRONG>int</STRONG>s for
       the  color value and for returning the red, green, and blue components,
       allowing a larger number of colors to be supported.


</PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
       The <STRONG>pair_content</STRONG> routine allows programmers to find out what  colors  a
       given  color-pair consists of.  It requires three arguments: the color-
       pair number, and two addresses of <STRONG>short</STRONG>s for storing the foreground and
       the background color numbers.

       <STRONG>o</STRONG>   The  first argument must be a legal color value, i.e., in the range
           <STRONG>1</STRONG> through <STRONG>COLOR_PAIRS-1</STRONG>, inclusive.

       <STRONG>o</STRONG>   The values that are stored at  the  addresses  pointed  to  by  the
           second  and  third  arguments  are  in  the range <STRONG>0</STRONG> through <STRONG>COLORS</STRONG>,
           inclusive.


</PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
       Because <STRONG>pair_content</STRONG> uses signed <STRONG>short</STRONG>s for its parameters, that limits
       color-pair and color-values to 32767 on modern hardware.  The extension
       <STRONG>extended_pair_content</STRONG> uses <STRONG>int</STRONG>s for the color pair  and  for  returning
       the  foreground  and  background  colors,  allowing  a larger number of
       colors to be supported.


</PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
       The extension <STRONG>reset_color_pairs</STRONG> tells ncurses to  discard  all  of  the
       color-pair  information  which was set with <STRONG>init_pair</STRONG>.  It also touches
       the current- and standard-screens, allowing an  application  to  switch
       color palettes rapidly.


</PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
       <STRONG>PAIR_NUMBER(</STRONG><EM>attrs</EM>)  extracts  the  color value from its <EM>attrs</EM> parameter
       and returns it as a color pair number.


</PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
       Its inverse <STRONG>COLOR_PAIR(</STRONG><EM>n</EM><STRONG>)</STRONG> converts a color pair number to an attribute.
       Attributes  can  hold color pairs in the range 0 to 255.  If you need a
       color pair larger than that, you must use functions  such  as  <STRONG>attr_set</STRONG>
       (which  pass  the  color  pair as a separate parameter) rather than the
       legacy functions such as <STRONG>attrset</STRONG>.


</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
       The routines <STRONG>can_change_color</STRONG> and <STRONG>has_colors</STRONG> return <STRONG>TRUE</STRONG> or <STRONG>FALSE</STRONG>.

       All other routines return the integer <STRONG>ERR</STRONG> upon failure and an <STRONG>OK</STRONG>  (SVr4
       specifies  only  "an  integer  value  other  than <STRONG>ERR</STRONG>") upon successful
       completion.

       X/Open defines no error conditions.   SVr4  does  document  some  error
       conditions which apply in general:

       <STRONG>o</STRONG>   This implementation will return <STRONG>ERR</STRONG> on attempts to use color values
           outside the range <STRONG>0</STRONG> to <STRONG>COLORS</STRONG>-1  (except  for  the  default  colors
           extension),   or   use   color   pairs   outside  the  range  <STRONG>0</STRONG>  to
           <STRONG>COLOR_PAIRS-1</STRONG>.

           Color values used in <STRONG>init_color</STRONG> must be in the range <STRONG>0</STRONG> to <STRONG>1000</STRONG>.

           An error is returned from all functions if  the  terminal  has  not
           been initialized.

           An  error is returned from secondary functions such as <STRONG>init_pair</STRONG> if
           <STRONG>start_color</STRONG> was not called.

       <STRONG>o</STRONG>   SVr4  does  much  the  same,  except  that  it  returns  <STRONG>ERR</STRONG>   from
           <STRONG>pair_content</STRONG>  if  the pair was not initialized using <STRONG>init_pairs</STRONG> and
           it returns <STRONG>ERR</STRONG> from <STRONG>color_content</STRONG> if the terminal does not  support
           changing colors.

           This implementation does not return <STRONG>ERR</STRONG> for either case.

       Specific functions make additional checks:

          <STRONG>init_color</STRONG>
               returns an error if the terminal does not support this feature,
               e.g., if the <STRONG>initialize_color</STRONG> capability  is  absent  from  the
               terminal description.

          <STRONG>start_color</STRONG>
               returns an error if the color table cannot be allocated.


</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
       In  the  <STRONG>ncurses</STRONG>  implementation,  there is a separate color activation
       flag, color palette, color  pairs  table,  and  associated  <STRONG>COLORS</STRONG>  and
       <STRONG>COLOR_PAIRS</STRONG>  counts  for  each  screen;  the  <STRONG>start_color</STRONG> function only
       affects the current screen.   The  SVr4/XSI  interface  is  not  really
       designed  with  this  in mind, and historical implementations may use a
       single shared color palette.

       Setting an implicit background color via  a  color  pair  affects  only
       character  cells  that  a character write operation explicitly touches.
       To change the background color used when parts of a window are  blanked
       by erasing or scrolling operations, see <STRONG><A HREF="curs_bkgd.3x.html">curs_bkgd(3x)</A></STRONG>.

       Several  caveats  apply  on  older x86 machines (e.g., i386, i486) with
       VGA-compatible graphics:

       <STRONG>o</STRONG>   COLOR_YELLOW is actually brown.  To get  yellow,  use  COLOR_YELLOW
           combined with the <STRONG>A_BOLD</STRONG> attribute.

       <STRONG>o</STRONG>   The  A_BLINK  attribute should in theory cause the background to go
           bright.  This often fails to work, and even some cards for which it
           mostly  works  (such  as the Paradise and compatibles) do the wrong
           thing when you try to set a bright "yellow" background (you  get  a
           blinking yellow foreground instead).

       <STRONG>o</STRONG>   Color RGB values are not settable.


</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
       SVr3.2 introduced color support to curses in 1987.

       SVr4  made  internal  changes,  e.g.,  moving the storage for the color
       state  from  <STRONG>SP</STRONG>  (the  <STRONG>SCREEN</STRONG>  structure)  to  <STRONG>cur_term</STRONG>  (the  <STRONG>TERMINAL</STRONG>
       structure), but provided the same set of library functions.

       SVr4  curses  limits  the  number of color pairs to 64, reserving color
       pair zero (0) as the terminal's initial uncolored  state.   This  limit
       arises  because  the color pair information is a bitfield in the <STRONG>chtype</STRONG>
       data type (denoted by <STRONG>A_COLOR</STRONG>).

       Other implementations of curses had different limits:

       <STRONG>o</STRONG>   PCCurses (1987-1990) provided for only eight (8) colors.

       <STRONG>o</STRONG>   PDCurses  (1992-present)  inherited  the  8-color  limitation  from
           PCCurses, but changed this to 256 in version 2.5 (2001), along with
           changing <STRONG>chtype</STRONG> from 16-bits to 32-bits.

       <STRONG>o</STRONG>   X/Open Curses (1992-present) added a new structure <STRONG>cchar_t</STRONG> to store
           the character, attributes and color-pair values, allowing increased
           range of color-pairs.  Both color-pairs  and  color-values  used  a
           signed <STRONG>short</STRONG>, limiting values to 15 bits.

       <STRONG>o</STRONG>   ncurses  (1992-present)  uses  eight  bits  for  <STRONG>A_COLOR</STRONG>  in <STRONG>chtype</STRONG>
           values.

           Version 5.3 provided a wide-character interface  (2002),  but  left
           color-pairs as part of the attributes-field.

           Since version 6 (2015), ncurses uses a separate <STRONG>int</STRONG> for color-pairs
           in the <STRONG>cchar_t</STRONG> values.  When those color-pair values fit in 8 bits,
           ncurses  allows  color-pairs  to  be  manipulated via the functions
           using <STRONG>chtype</STRONG> values.

       <STRONG>o</STRONG>   NetBSD curses used  6  bits  from  2000  (when  colors  were  first
           supported)  until  2004.   At  that point, NetBSD changed to use 10
           bits.  As of 2021, that size is  unchanged.   Like  ncurses  before
           version  6,  the  NetBSD  color-pair  information  is stored in the
           attributes field of <STRONG>cchar_t</STRONG>, limiting the number of color-pairs  by
           the size of the bitfield.


</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>

</PRE><H3><a name="h3-Extensions">Extensions</a></H3><PRE>
       The  functions  marked as extensions were designed for <STRONG><A HREF="ncurses.3x.html">ncurses(3x)</A></STRONG>, and
       are not found in SVr4 curses, 4.4BSD  curses,  or  any  other  previous
       version of curses.


</PRE><H3><a name="h3-Standards">Standards</a></H3><PRE>
       This  implementation satisfies XSI Curses's minimum maximums for <STRONG>COLORS</STRONG>
       and <STRONG>COLOR_PAIRS</STRONG>.

       The  <STRONG>init_pair</STRONG>  routine  accepts  negative  values  of  foreground  and
       background  color  to support the <STRONG><A HREF="default_colors.3x.html">use_default_colors(3x)</A></STRONG> extension, but
       only if that routine has been first invoked.

       The assumption that <STRONG>COLOR_BLACK</STRONG> is the default background color for all
       terminals   can   be   modified   using  the  <STRONG><A HREF="default_colors.3x.html">assume_default_colors(3x)</A></STRONG>
       extension.

       This implementation checks the pointers, e.g., for the values  returned
       by  <STRONG>color_content</STRONG>  and  <STRONG>pair_content</STRONG>,  and will treat those as optional
       parameters when null.

       X/Open Curses does not specify a limit for the  number  of  colors  and
       color pairs which a terminal can support.  However, in its use of <STRONG>short</STRONG>
       for the parameters, it carries over SVr4's  implementation  detail  for
       the compiled terminfo database, which uses signed 16-bit numbers.  This
       implementation provides extended versions of those functions which  use
       <STRONG>short</STRONG>  parameters, allowing applications to use larger color- and pair-
       numbers.

       The <STRONG>reset_color_pairs</STRONG> function is an extension of ncurses.


</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
       <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>,   <STRONG><A HREF="curs_initscr.3x.html">curs_initscr(3x)</A></STRONG>,   <STRONG><A HREF="curs_attr.3x.html">curs_attr(3x)</A></STRONG>,    <STRONG><A HREF="curs_variables.3x.html">curs_variables(3x)</A></STRONG>,
       <STRONG><A HREF="default_colors.3x.html">default_colors(3x)</A></STRONG>



ncurses 6.4                       2023-09-16                    <STRONG><A HREF="curs_color.3x.html">curs_color(3x)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a>
<ul>
<li><a href="#h3-Overview">Overview</a></li>
<li><a href="#h3-Color-Rendering">Color Rendering</a></li>
</ul>
</li>
<li><a href="#h2-CONSTANTS">CONSTANTS</a></li>
<li><a href="#h2-VARIABLES">VARIABLES</a>
<ul>
<li><a href="#h3-COLORS">COLORS</a></li>
<li><a href="#h3-COLOR_PAIRS">COLOR_PAIRS</a></li>
</ul>
</li>
<li><a href="#h2-FUNCTIONS">FUNCTIONS</a>
<ul>
<li><a href="#h3-start_color">start_color</a></li>
<li><a href="#h3-has_colors">has_colors</a></li>
<li><a href="#h3-can_change_color">can_change_color</a></li>
<li><a href="#h3-init_pair">init_pair</a></li>
<li><a href="#h3-init_extended_pair">init_extended_pair</a></li>
<li><a href="#h3-init_color">init_color</a></li>
<li><a href="#h3-init_extended_color">init_extended_color</a></li>
<li><a href="#h3-color_content">color_content</a></li>
<li><a href="#h3-extended_color_content">extended_color_content</a></li>
<li><a href="#h3-pair_content">pair_content</a></li>
<li><a href="#h3-extended_pair_content">extended_pair_content</a></li>
<li><a href="#h3-reset_color_pairs">reset_color_pairs</a></li>
<li><a href="#h3-PAIR_NUMBER">PAIR_NUMBER</a></li>
<li><a href="#h3-COLOR_PAIR">COLOR_PAIR</a></li>
</ul>
</li>
<li><a href="#h2-RETURN-VALUE">RETURN VALUE</a></li>
<li><a href="#h2-NOTES">NOTES</a></li>
<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a>
<ul>
<li><a href="#h3-Extensions">Extensions</a></li>
<li><a href="#h3-Standards">Standards</a></li>
</ul>
</li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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